nilfs2: convert ifile to use kmap_local

nilfs2: convert ifile to use kmap_local

Convert deprecated kmap() and kmap_atomic() to use kmap_local for the
ifile metadata file used to manage disk inodes.

In some usages, calls to kmap_local and kunmap_local are split into
different helpers, but those usages can be safely changed to local thread
kmap.

Link: https://lkml.kernel.org/r/20240122140202.6950-11-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>